An adjustment shim for the drive pulley shaft of a Citroën 11CV is a thin spacer used to achieve the correct tension and alignment levels of the drive pulley shaft. These shims are crucial for maintaining optimal operation of the pulley and belt systems, reducing wear, and ensuring smooth engine operation. Made from carefully selected materials for durability, these shims play a key role in absorbing vibrations and minimizing noise. Specifically designed for the classic Citroën 11CV, they help in preserving vehicle performance as if new.